The present invention relates to a laser device for projecting a structured light pattern onto a scene using several arrays of semiconductor lasers, in particular vertical cavity surface emitting lasers (VCSELs). Structured light patterns projected onto a scene and observed with a camera enable the extraction of 3D information by image processing. Such a method is applied e. g. in the Microsoft Kinect™ game console and recently discussed for industrial applications, especially in the automotive field. In this field the new EU-NCAP safety norm enforces a distance measurement which is able to detect pedestrians and provides a resolution which allows autonomous measures taken by the car system.
The required structured light pattern can be generated by dedicated micro-optical systems like micro-lens arrays or diffractive optical elements (DOE) which are illuminated by a laser, e. g. by an array of VCSELs. An example is shown in US 2012/051588 A1, which discloses a laser device for projecting a structured light pattern onto a scene using at least one VCSEL array. The light from the VCSEL array is focused through a collimating micro-lens array which directs the beams from the VCSEL array to a DOE. The DOE forms the beams into a variety of light patterns which then enable the desired 3D imaging.
These known optical systems suffer from a loss in brightness and optical efficiency mainly because of two reasons. They are illuminated with an average brightness always lower than the maximum brightness of the laser source and their fill factor is limited since the need for a randomized pattern requires a non dense packing. Furthermore the maximum contrast between bright and dark regions is low.